Unlike traditional tennis ball launchers, this tennis robot hits with an actual racket. This makes judging when the ball is hit and where it will land a whole lot easier.

The balls are launched between 20kph (12.4mph) and 70kph (43mph), which isn't that fast, but is good enough for practice. Seriously, as a guy who's been hit in the nuts more than once by a tennis ball machine (ball me once, shame on you, b..ba....I'm not gonna get balled again), I can say this is a good invention. – Jason Chen